A typical wireless communication system comprises a plurality of wireless communications devices exchanging data with each other. In some wireless communication systems, for example, infrastructure networks, the system may further comprise a wireless base station for managing communications between the wireless communications devices. In other words, each intra-system communication would be exchanged via the wireless base station. In other wireless communication systems, for example, mesh networks and ad hoc wireless networks, the wireless base station may be omitted, i.e. the wireless communications devices may communicate directly with each other.
In certain advantageous wireless communication systems, the transmitted data is packetized. More specifically, the data is formatted into groups of packets for transmission. Each group of packets is transmitted via a forward transmission, which is comprised of a preamble portion and a body portion associated therewith, i.e. a forward transmission block. The body portion is commonly known as the payload and typically comprises user generated data, i.e. groups of packets. The preamble portion may include control information. The control information may contain information the wireless communication system uses to deliver the user data, for example, source and destination addresses, error detection codes such as checksums, sequencing information, and synchronization information. As will be appreciated by those skilled in the art, the preamble portion may include a synchronization sequence for the synchronization information.
In the typical wireless communication system, the preamble portion may have a fixed length. The typical wireless communication system may employ a preamble portion having a minimum length to accommodate for the most difficult transmission scenario, i.e. poor transmission channel and a variety of low latency data services. For example, the most difficult transmission scenario may comprise receiving 75 bits per second with a signal-to-noise ratio of −10 dB with NATO Standardization Agreement (STANAG) 4415 channel conditions. A potential drawback to this approach is that it increases the overhead of the wireless communication system to unnecessary levels for nominal transmissions, i.e. a greater percentage of each forward transmission block is used for control information. Another approach is to choose a preamble portion length capable of accommodating the mean transmission scenario. A potential drawback to this approach is that more problematic transmission scenarios may exceed the capabilities of the preamble portion, i.e. the transmission fails.
An approach is disclosed in U.S. Pat. No. 6,014,385 to Ayanoglu et al. This method includes transmitting a training sequence for synchronization and equalization prior to transmitting a forward transmission. The length of the training sequence may vary from terminal-to-terminal and temporally and based upon whether the terminals are fixed or mobile, the modulation scheme used, the carrier frequency, the bit error rate of previous transmissions, and the weather and topology of the terrain near the terminals. A drawback to this approach may be that synchronization sequences must be propagated throughout the network to be used.